Vegetable Fertilizer Will Typical Vegetable Plant Fertilizer Increase The Nitrogen In The Soil?

Will typical vegetable plant fertilizer increase the nitrogen in the soil? - vegetable fertilizer

I am growing vegetables and take the yellow leaves on some plants and also get black rot area at the end of my some of my zucchini. I mean, it is caused by a lack of nitrogen.

What can you tell me to save on fertilizer? Can she give the nitrogen in plants and everything would be cool?